345
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
A Key Parameter for Strength Control of Lightweight Cemented Clays
Un paramètre clé pour le contrôle des forces de légères argiles cimentées
Horpibulsuk S., Suddeepong A., Chinkulkijniwat A.
School of Civil Engineering, Suranaree University of Technology, Nakhon Ratchasima, Thailand
ABSTRACT: Lightweight cemented clays have wide applications in the infrastructure rehabilitation and in the construction of new
facilities. The void/cement ratio,
V
/
C
, which is defined as the ratio of the void volume of clay to the cement volume, is proved as the
prime parameter governing the strength and compression characteristics of lightweight cemented clays. The fabric (arrangement of
clay particles, clusters and pore spaces) reflected from both air foam content and water content is taken into consideration by the void
volume while the inter-particle forces (levels of cementation bond) are governed by the input of cement (cement volume). Three types
of clay namely, kaolin, Bangkok clay and bentonite as representatives of non- to high swelling clays were used in this study. A
strength equation in terms of
V
/
C
at a particular curing time is introduced using Abram’s law as a basis.
RÉSUMÉ : Les légères argiles cimentées ont de larges applications dans la réhabilitation des infrastructures et de la construction de
nouvelles installations. Le rapport de vide/ciment,
V
/
C
, qui est défini comme le rapport du volume de vide de l’argile au volume de
ciment, comme le prouve le paramètre premier régir la force et les caractéristiques de compression des argiles légères cémentées. Le
tissu (arrangement de particules d’argile, des grappes et des espaces de pores) à la fois réfléchie par le contenu de mousse à air et la
teneur en eau est prise en compte par le volume de vide, tandis que les forces inter-particulaires (niveaux de liaison cémentation) sont
régis par l’entrée de ciment (cimenter volume). Trois types d’argile, à savoir le kaolin, l’argile de Bangkok et la bentonite en tant que
représentants d’une quantité d’argiles gonflantes ont été utilisés dans cette étude. Une équation de la force en termes de
V
/
C
à un
temps de durcissement particulier est introduite par la loi d’Abram comme base.
KEYWORDS: compressibility, lightweight cemented clay strength, void/cement ratio.
1 INTRODUCTION
When infrastructures such as road embankments and bridge
foundations are constructed on soft soil deposits, several
geotechnical engineering problems are encountered. These
deposits tend to consolidate and undergo large vertical
settlement and lateral deformation during and after construction
due to incumbent loads. The use of lightweight materials with
unit weight of 8 to 12 kn/m
3
and moderate to high strength as a
backfill material to reduce the weight of the structure on the soft
clay is an effective means. Lightweight materials have wide
applications in the infrastructure rehabilitation and in the
construction of new facilities. They can be used as a backfill for
quay walls and bridge abutments to reduce the earth pressure
behind the wall, as a fill for construction of embankments on
soft soil to reduce overburden pressure, as a method of reducing
pressure on the tunnel lining.
For soft clay admixed with cement, the clay-water/cement
ratio,
w
c
/
C
was proved as the prime parameter governing
engineering properties (Miura et al., 2001; Horpibulsuk and
Miura, 2001 and Horpibulsuk et al., 2005). Horpibulsuk et al.
(2003; 2011a, b and 2012) successfully employed this
parameter to develop a generalized strength equation based on
Abrams’ law (Abrams, 1918). The equation is useful for
laboratory mix design. This parameter was also successfully
used to predict the strength development in cement stabilized
coarse-grained soils on the wet side of optimum water content
wherein the degree of saturation is higher than 80%
(Horpibulsuk et al. 2006 and Chinkulkijniwat and Horpibulsuk,
2012). Consoli et al. (2007) extended the clay-water/cement
ratio hypothesis to analyze the strength development in
compacted (unsaturated) cement-stabilized sand. They proposed
a key parameter taking the role of air bubble in pore space
(void) on the strength development into account. The parameter
was designated as void/cement ratio,
V
/
C
and was defined as the
ratio of absolute volume of void (water and air) to absolute
volume of cement of the compacted sand.
Even though the cement stabilized soil have very low water
content due to compaction effect, it is composed of water, air,
soil solid and cement, which is the same as lightweight cement
clay. The modified clay-water/cement ratio (void/cement ratio,
V
/
C
), is thus considered to describe the engineering properties
of lightweight cemented clays which possess very high water
contents in this study. Three types of clay namely, kaolin,
Bangkok clay and bentonite as representatives of non- to high
swelling clays were used for this objective. Finally, the strength
equation is proposed based on the parameter
V
/
C.
2 MATERIALS AND METHODS
Bangkok clay was collected from Bangkok Noi district,
Bangkok, Thailand at a 3 meter depth. Kaolin and bentonite
were obtained from a commercial company. Bangkok clay was
composed of 2% sand, 39% silt and 55% clay. The natural
water content was 78% and the specific gravity was 2.64. The
liquid and plastic limits were 73% and 31%, respectively. Based
on the Unified Soil Classification System (USCS), the clay was
classified as inorganic clay of high plasticity (CH).
Groundwater was had a depth of about 1.0 m from surface. The
undrained shear strength was 12 kPa. Kaolin was composed of
0% sand, 22% silt and 78% clay. The specific gravity was 2.65.
The liquid and plastic limits were 46% and 36%, respectively.
The clay was classified as inorganic clay of low plasticity (CL)
